Medical devices

ABSTRACT

In some embodiments, a method can include delivering an electrically conductive coil into a lumen of a subject. In certain embodiments, the method can further include delivering at least a portion of an endoprosthesis into a lumen of the electrically conductive coil. In some embodiments, the method may enhance the MRI visibility of material within a lumen of the endoprosthesis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of, and claims priority under35 U.S.C. § 120 to, U.S. patent application Ser. No. 11/198,961, filedon Aug. 8, 2005, which is incorporated herein by reference in itsentirety.

TECHNICAL FIELD

The invention relates to medical devices, and to related components andmethods.

BACKGROUND

The body includes various passageways such as arteries, other bloodvessels, and other body lumens. These passageways sometimes becomeoccluded or weakened. For example, the passageways can be occluded by atumor, restricted by plaque, or weakened by an aneurysm. When thisoccurs, the passageways can be reopened or reinforced, or even replaced,with a medical endoprosthesis. An endoprosthesis is typically a tubularmember that is placed in a lumen in the body. Examples of endoprosthesesinclude stents, stent-grafts, and covered stents.

An endoprosthesis can be delivered inside the body by a catheter thatsupports the endoprosthesis in a compacted or reduced-size form as theendoprosthesis is transported to a desired site. Upon reaching the site,the endoprosthesis is expanded, for example, so that it can contact thewalls of the lumen.

When the endoprosthesis is advanced through the body, its progress canbe monitored (e.g., tracked), so that the endoprosthesis can bedelivered properly to a target site. After the endoprosthesis has beendelivered to the target site, the endoprosthesis can be monitored todetermine whether it has been placed properly and/or is functioningproperly.

Methods of tracking and monitoring a medical device include X-rayfluoroscopy and magnetic resonance imaging (MRI). MRI is a non-invasivetechnique that uses a magnetic field and pulsed radio waves to image thebody. In some MRI procedures, the patient is exposed to a staticmagnetic field, which interacts with certain atoms (e.g., hydrogenatoms) within the magnetic field (e.g., in the patient's body), causingthe spins of the atoms' nuclei to become aligned relative to themagnetic field. Incident radio waves are then directed at the patient.The incident radio waves interact with atoms in the patient's bodyhaving a similar resonance frequency as the incident radio waves,thereby causing the atoms' nuclei to assume a temporary non-alignedhigh-energy state. After the incident radio pulse stops, the decay ofthe spins in these atomic nuclei to lower energy levels producescharacteristic return radio waves. The return radio waves are detectedby a scanner and processed by a computer to generate an image of thebody.

SUMMARY

In one aspect, the invention features a method that includes deliveringan electrically conductive coil into a lumen of a subject, anddelivering at least a portion of an endoprosthesis into a lumen of theelectrically conductive coil.

Embodiments can include one or more of the following features.

The method can include using a generally tubular member to deliver theelectrically conductive coil into the lumen of the subject. In someembodiments, the electrically conductive coil can be attached to thegenerally tubular member. For example, in certain embodiments, aproximal end and/or a distal end of the electrically conductive coil canbe attached to the generally tubular member. Delivering the electricallyconductive coil into a lumen of a subject may include separating (e.g.,electrolytically detaching, mechanically detaching) an attached end(e.g., a proximal end, a distal end) of the electrically conductive coilfrom the generally tubular member. In some embodiments, the electricallyconductive coil can be attached to the generally tubular member by abioerodible material. The method may include detaching the electricallyconductive coil from the generally tubular member by eroding thebioerodible material.

During delivery of the electrically conductive coil into the lumen ofthe subject, the electrically conductive coil can be supported by thegenerally tubular member. In some embodiments, the method can includeseparating the electrically conductive coil from the generally tubularmember so that the electrically conductive coil no longer is supportedby the generally tubular member. The electrically conductive coil may beseparated from the generally tubular member by rotating the generallytubular member, and/or by expanding the electrically conductive coilinto the lumen of the subject.

Delivering an electrically conductive coil into a lumen of a subject caninclude delivering a sheath containing the electrically conductive coilinto the lumen of the subject. In some embodiments, the method caninclude rotating the sheath to deliver the electrically conductive coilfrom the sheath into the lumen of the subject. In certain embodiments,the method can include proximally withdrawing the sheath. The interiorsurface of the sheath can contact the electrically conductive coil. Insome embodiments, the interior surface of the sheath can have at leastone groove, such as a helical groove. In certain embodiments (e.g., incertain embodiments in which the groove is a helical groove), theelectrically conductive coil can be disposed within the groove. In someembodiments, the interior surface of the sheath may not have anygrooves.

The method can include establishing electrical communication between aproximal end and a distal end of the electrically conductive coil. Theelectrical communication can be established using a solid conductor,such as a wire, or without using a solid conductor.

The method can include using magnetic resonance imaging to view anenvironment surrounding the electrically conductive coil prior todelivering at least a portion of an endoprosthesis into a lumen of theelectrically conductive coil.

The electrically conductive coil can include a first capacitor, and themethod can include flowing an electrical current through a circuitincluding the first capacitor. The electrical circuit can include atleast two capacitors. During delivery of the electrically conductivecoil into the lumen, the electrically conductive coil can be in contactwith at least one electrical circuit component that is not a componentof the electrically conductive coil. During delivery of the electricallyconductive coil into the lumen, the electrically conductive coil canresonate at the Larmor frequency of a proton in a one Tesla magneticfield, a 1.5 Tesla magnetic field, or a three Tesla magnetic field.

The method can include expanding the endoprosthesis and/or viewing theendoprosthesis using magnetic resonance imaging.

The electrically conductive coil can form a resonance circuit. Theresonance circuit can include at least one capacitor. In someembodiments, the capacitor can be supported by, and/or included in, theendoprosthesis. In certain embodiments, the capacitor may not besupported by the endoprosthesis, and/or may not be included in theendoprosthesis. The electrically conductive coil can include a conductor(e.g., a wire) connecting one section of the electrically conductivecoil to another section of the electrically conductive coil. In someembodiments, the electrically conductive coil can include a conductor(e.g., a wire) connecting a proximal end of the electrically conductivecoil to a distal end of the electrically conductive coil. In certainembodiments, the method can include connecting a proximal end of theelectrically conductive coil to a distal end of the electricallyconductive coil using a conductor (e.g., a wire).

The electrically conductive coil can include a superelastic materialand/or a shape memory material. In some embodiments, the electricallyconductive coil can include Nitinol.

The electrically conductive coil can be a self-expanding coil and/or aballoon-expandable coil.

The endoprosthesis can be a stent (e.g., a self-expanding stent, aballoon-expandable stent), a graft, a stent-graft, or a covered stent.

Embodiments may include one or more of the following advantages.

An electrically conductive coil can be relatively efficiently deliveredto a target site, such as a lumen of a subject. In some embodiments, anelectrically conductive coil can be delivered to a target site using adelivery device (e.g., a generally tubular member) to which theelectrically conductive coil is attached. In certain embodiments, theelectrically conductive coil can be attached to the delivery device by abioerodible material. One or more body fluids (e.g., blood) at thetarget site can erode the bioerodible material and help to detach thecoil from the delivery device.

In certain embodiments, an electrically conductive coil can be withdrawnback into a delivery device after being partially delivered from thedelivery device. For example, in some embodiments in which anelectrically conductive coil is partially delivered from a deliverydevice by rotating and withdrawing a sheath of the delivery device, thesheath can be rotated in the opposite direction to recapture the coil.It may be desirable to recapture a coil if, for example, the coil hasmistakenly been delivered to a non-target site in the body of a subject.

In some embodiments, an electrically conductive coil can be adapted foruse with multiple different types of endoprostheses. For example, anelectrically conductive coil may be adapted for use with anendoprosthesis having one configuration, and with an endoprosthesishaving a different configuration.

In certain embodiments, MRI, a non-invasive procedure, can be used toview material within the lumen of an endoprosthesis that is at leastpartially disposed within an electrically conductive coil. Thus, anoperator (e.g., a physician) can assess the condition of a target site(e.g., for signs of restenosis) after implantation of the endoprosthesis(e.g., two weeks after implantation, one month after implantation). Insome embodiments (e.g., in some embodiments in which an electricallyconductive coil forms a resonance circuit), an electrically conductivecoil can enhance the MRI visibility of material within the lumen of theendoprosthesis. In certain embodiments in which an electricallyconductive coil forms a resonance circuit, the electrically conductivecoil may increase the temperature of its immediate environment, but maynot significantly increase the temperature of the rest of the body ofthe subject.

In some embodiments, an electrically conductive coil can be used both asan imaging coil (e.g., to provide an image of a lumen during delivery ofthe coil to a target site) and as a resonance circuit (e.g., once thecoil has been delivered to a target site). Thus, the same electricallyconductive coil can be used for multiple different purposes during oneprocedure.

Other aspects, features, and advantages are in the description,drawings, and claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is an illustration of an embodiment of an endoprosthesis disposedwithin an embodiment of an electrically conductive coil in a lumen of asubject.

FIG. 2 is a perspective view of the endoprosthesis of FIG. 1.

FIG. 3 is a side view of the electrically conductive coil of FIG. 1.

FIG. 4 is a schematic illustration of an embodiment of a resonancecircuit.

FIG. 5A is an illustration of a embodiment of a coil delivery systemwithin a lumen of a subject.

FIGS. 5B and 5C are illustrations of the coil delivery system of FIG.5A, during delivery of an embodiment of an electrically conductive coilinto the lumen of the subject.

FIG. 5D is an illustration of the electrically conductive coil of FIGS.5B and 5C, once the electrically conductive coil has been delivered intothe lumen of the subject.

FIG. 5E is an illustration of an embodiment of an endoprosthesisdisposed within the electrically conductive coil of FIGS. 5B-5D.

FIG. 6A is an illustration of an embodiment of a coil delivery systemwithin a lumen of a subject.

FIG. 6B is an enlarged view of region 6B of FIG. 6A.

FIG. 6C is an illustration of the coil delivery system of FIG. 6A,during delivery of an embodiment of an electrically conductive coil intothe lumen of the subject.

FIG. 6D is an illustration of the electrically conductive coil of FIG.6C, once the electrically conductive coil has been delivered into thelumen of the subject.

FIG. 6E is an illustration of an embodiment of an endoprosthesisdisposed within the electrically conductive coil of FIGS. 6C and 6D.

FIG. 7 is a side perspective view of the electrically conductive coil ofFIGS. 6C-6E.

FIG. 8A is an illustration of an embodiment of a coil delivery systemwithin a lumen of a subject.

FIG. 8B is an illustration of the coil delivery system of FIG. 8A,during delivery of an embodiment of an electrically conductive coil intothe lumen of the subject.

FIG. 8C is an illustration of the electrically conductive coil of FIG.8B, once the electrically conductive coil has been delivered into thelumen of the subject.

FIG. 8D is an illustration of an embodiment of an endoprosthesisdisposed within the electrically conductive coil of FIGS. 8B and 8C.

FIG. 9 is a side perspective view of the electrically conductive coil ofFIGS. 8B-8D.

FIG. 10 is a side view of an embodiment of a coil delivery system.

FIG. 11A is a perspective view of an embodiment of a coil deliverysystem.

FIG. 11B is a cross-sectional view of the coil delivery system of FIG.11A, taken along line 11B-11B.

FIG. 12 is a side perspective view of an embodiment of a coil deliverysystem and an embodiment of an electrically conductive coil.

FIG. 13A is an illustration of a embodiment of a coil delivery systemwithin a lumen of a subject.

FIGS. 13B and 13C are illustrations of the coil delivery system of FIG.13A, during delivery of an embodiment of an electrically conductive coilinto the lumen of the subject.

FIGS. 14A and 14B illustrate the delivery of an embodiment of anelectrically conductive coil into the lumen of a subject.

FIG. 15A is an illustration of an embodiment of a coil delivery systemand an embodiment of an electrically conductive coil within a lumen of asubject.

FIG. 15B is an illustration of the coil delivery system and electricallyconductive coil of FIG. 15A, during delivery of the electricallyconductive coil into the lumen of the subject.

FIG. 15C is an illustration of the electrically conductive coil of FIG.15A, once the electrically conductive coil has been delivered into thelumen of the subject.

FIG. 15D is an enlarged view of a portion of the coil delivery systemand the electrically conductive coil of FIG. 15A.

FIG. 16A is an illustration of an embodiment of a coil delivery systemand an embodiment of an electrically conductive coil, disposed within alumen of a subject.

FIG. 16B is an illustration of the coil delivery system and theelectrically conductive coil of FIG. 16A, during delivery of theelectrically conductive coil into the lumen of the subject.

FIG. 17 is an illustration of an embodiment of a coil delivery systemand an embodiment of an electrically conductive coil, disposed within alumen of a subject.

FIG. 18 is an illustration of an embodiment of a coil delivery systemand an embodiment of an electrically conductive coil, disposed within alumen of a subject.

FIG. 19A is an illustration of an embodiment of a coil delivery systemand an embodiment of an electrically conductive coil, disposed within alumen of a subject.

FIG. 19B is an illustration of the coil delivery system and theelectrically conductive coil of FIG. 19A, during delivery of theelectrically conductive coil into the lumen of the subject.

FIG. 19C is an illustration of the electrically conductive coil of FIGS.19A and 19B, once the electrically conductive coil has been deliveredinto the lumen of the subject.

FIG. 20 is a side view of an embodiment of an electrically conductivecoil.

FIG. 21 is a side view of an embodiment of an electrically conductivecoil.

FIG. 22 is a side view of an embodiment of an electrically conductivecoil.

FIG. 23A is an illustration of an embodiment of a coil delivery systemand an embodiment of an electrically conductive coil, disposed within alumen of a subject.

FIG. 23B is an illustration of the coil delivery system and theelectrically conductive coil of FIG. 23A, after the electricallyconductive coil has been delivered into the lumen of the subject.

FIG. 24 is a cross-sectional view of an embodiment of a coil deliverysystem and an embodiment of an electrically conductive coil.

DETAILED DESCRIPTION

Referring to FIG. 1, an electrically conductive coil 10 is disposedwithin a lumen 12 of a subject. Coil 10 has a proximal end 14 and adistal end 16, which are connected to each other by a wire 18. A stent20, which includes a lumen 22 (FIG. 2) is disposed within a lumen 24(FIG. 3) of coil 10.

The structure of a stent such as stent 20 may adversely affect theMRI-visibility of material within the lumen of the stent. Withoutwishing to be bound by theory, it is believed that in some embodiments,when a stent is exposed to a variable magnetic field during MRI, thestent can induce a current that limits the visibility of material withinthe lumen of the stent. Specifically, during MRI, an incidentelectromagnetic field is applied to a stent. The magnetic environment ofthe stent can be constant or variable, such as when the stent moveswithin the magnetic field (e.g., from a beating heart) or when theincident magnetic field is varied. When there is a change in themagnetic environment of the stent, which can act as a coil or asolenoid, an induced electromotive force (emf) is generated, accordingto Faraday's Law. The induced emf in turn can produce an eddy currentthat induces a magnetic field that opposes the change in magnetic field.The induced magnetic field can oppose the incident magnetic field,thereby reducing (e.g., distorting) the visibility of material in thelumen of the stent. A similar effect can be caused by a radiofrequencypulse applied during MRI. Thus, the ability to use MRI to view andassess the condition of a target site that includes a stent such asstent 20 can be limited.

Coil 10 can help to increase the MRI visibility of material within lumen22 of stent 20. Coil 10 forms a resonance circuit that is tuned to theRF frequency of the MRI system that is used to view stent 10. FIG. 4shows a schematic illustration of a resonance circuit 50, which includesan inductor 54, a resistor 56, and a capacitor 58. In some embodiments,coil 10 can form an inductor, and/or a capacitor (e.g., capacitor 58)can be applied (e.g., stamped) onto coil 10, and/or can be embedded intocoil 10. In certain embodiments, capacitor 58 of resonance circuit 50may be a part of stent 20 (e.g., may be carried by stent 20), or may notbe a part of stent 20 (e.g., may not be carried by stent 20). Withoutwishing to be bound by theory, it is believed that the presence of aresonance circuit such as coil 10 in the vicinity of stent 20 can helpto at least partially reduce the effect of the above-described inducedmagnetic field. When stent 20 is viewed using MRI, coil 10 can locallyenhance (e.g., amplify) the RF field that is generated by the MRIsystem. Thus, coil 10 can be used to increase the RF energy levellocally (near stent 20), without also significantly increasing the RFenergy level in the rest of the body of the subject. This can, forexample, limit the likelihood of a significant increase in thetemperature of the rest of the body of the subject. The increase in RFenergy level near stent 20 can increase the visibility of materialwithin lumen 22 of stent 20. Resonance circuits are further described,for example, in Melzer et al., U.S. Pat. No. 6,280,385.

A coil such as coil 10 can be delivered into lumen 12 using any of anumber of different methods.

For example, FIGS. 5A through 5E illustrate the delivery of coil 10 intolumen 12 using a delivery device 100. Delivery device 100 can be, forexample, a catheter system, such as one of the catheter systemsdescribed below. As shown in FIG. 5A, delivery device 100 includes agenerally tubular inner member 102, a tip 104 at the distal end 106 ofinner member 102, and a sheath 108 surrounding inner member 102. Coil10, which is formed of a superelastic material, is loaded onto innermember 102, and is restrained on inner member 102 by two bioerodiblestrips 110 and 112.

Referring to FIG. 5B, to deliver coil 10 into lumen 12, sheath 108 isretracted proximally (in the direction of arrow A), exposing innermember 102. Over time, bioerodible strips 110 and 112 erode (e.g., as aresult of being exposed to blood and/or other body fluids in lumen 12).As shown in FIG. 5C, bioerodible strips 110 and 112 eventually erodesufficiently to allow coil 10 to expand away from inner member 102 andinto lumen 12.

Referring now to FIG. 5D, during and/or after expansion of coil 10,delivery device 100 is retracted from lumen 12, leaving coil 10 in lumen12. Referring to FIG. 5E, stent 20 is then delivered into lumen 24 (FIG.5D) of coil 10. Stent 20 can be delivered into lumen 24 and expandedwithin lumen 24 using, for example, a stent delivery system such as acatheter system. Examples of catheter systems include self-expandablestent delivery systems, and balloon catheter systems, such assingle-operator exchange catheter systems, over-the-wire cathetersystems, and fixed-wire catheter systems. Single-operator exchangecatheters are described, for example, in Keith, U.S. Pat. No. 5,156,594,and in Stivland et al., U.S. Pat. No. 6,712,807. Over-the-wire cathetersare described, for example, in Schoenle et al., U.S. Patent ApplicationPublication No. US 2004/0131808 A1, published on Jul. 8, 2004.Fixed-wire catheters are described, for example, in Segar, U.S. Pat. No.5,593,419. Catheter systems are also described in, for example, Wang,U.S. Pat. No. 5,195,969, and Hamlin, U.S. Pat. No. 5,270,086. Examplesof commercially available balloon catheters include the Monorail™ familyof balloon catheters (Boston Scientific Scimed, Inc., Maple Grove,Minn.). Stents and stent delivery are also exemplified by the Radius® orSymbiot® systems (Boston Scientific Scimed, Inc., Maple Grove, Minn.).

Bioerodible strips 110 and 112 each can include one or more bioerodiblematerials. In some embodiments, bioerodible strips 110 and 112 caninclude one or more of the same bioerodible materials. Examples ofbioerodible materials include non-metallic bioerodible materials, suchas polysaccharides (e.g., alginate); alginate salts (e.g., sodiumalginate); sugars (e.g., sucrose (C₁₂H₂₂O₁₁), dextrose (C₆H₁₂O₆),sorbose (C₆H₁₂O₆)); sugar derivatives (e.g., glucosamine (C₆H₁₃NO₅),sugar alcohols such as mannitol (C₆H₁₄O₆)); inorganic, ionic salts(e.g., sodium chloride (NaCl), potassium chloride (KCl), sodiumcarbonate (Na₂CO₃)); water-soluble polymers (e.g., a polyvinyl alcohol,such as a polyvinyl alcohol that has not been cross-linked);biodegradable poly DL-lactide-poly ethylene glycol (PELA); hydrogels(e.g., polyacrylic acid, hyaluronic acid, gelatin, carboxymethylcellulose); polyethylene glycol (PEG); chitosan; polyesters (e.g., apolycaprolactone); and poly(lactic-co-glycolic) acids (e.g., apoly(d-lactic-co-glycolic) acid).

Other examples of bioerodible materials include bioerodiblepolyelectrolytes, such as heparin, polyglycolic acid (PGA), polylacticacid (PLA), polyamides, poly-2-hydroxy-butyrate (PHB), polycaprolactone(PCL), poly(lactic-co-glycolic)acid (PLGA), protamine sulfate,polyallylamine, polydiallyldimethylammonium species (e.g.,poly(diallyl-dimethylammonium chloride) (PDADMA, Aldrich)),polyethyleneimine, chitosan, eudragit, gelatin, spermidine, albumin,polyacrylic acid, sodium alginate, poly(styrene sulfonate) (PSS,Scientific Polymer Products), hyaluronic acid, carrageenan, chondroitinsulfate, carboxymethylcellulose, polypeptides, proteins, DNA, andpoly(N-octyl-4-vinyl pyridinium iodide) (PNOVP). Polyelectrolytes aredescribed, for example, in Tarek R. Farhat and Joseph B. Schlenoff,“Corrosion Control Using Polyelectrolyte Multilayers”, Electrochemicaland Solid State Letters, 5 (4) B13-B15 (2002), and in Weber, U.S. patentapplication Ser. No. 11/127,968, filed on May 12, 2005, and entitled“Medical Devices and Methods of Making the Same”. Bioerodible materialsare described, for example, in Colen et al., U.S. Patent ApplicationPublication No. US 2005/0192657 A1, published on Sep. 1, 2005, andentitled “Medical Devices”.

As another example, FIGS. 6A-6E illustrate a method of delivering a coil200 into a lumen 204 of a subject using a delivery system 202. As shownin FIG. 6A, delivery system 202 is formed of a generally tubular member206 with a tip 208. Coil 200, which is formed of a shape memorymaterial, is supported by generally tubular member 206. The proximal end210 of coil 200 is attached to generally tubular member 206 by abioerodible connector 212, and the distal end 214 of coil 200 isattached to generally tubular member 206 by a bioerodible connector 216(shown in an enlarged view in FIG. 6B). Bioerodible connector 212 isformed of a different material from bioerodible connector 216. As shownin FIG. 6C, bioerodible connector 216 erodes before bioerodibleconnector 212, so that coil 200 first starts to expand away fromgenerally tubular member 206 at its distal end 214. To aid in theexpansion and placement of coil 200 in lumen 204, delivery system 202 isrotated in the direction of arrow A1 and is withdrawn proximally (in thedirection of arrow A2). The rotation of delivery system 202 in thedirection of arrow A1 can help to force coil 200 against the wall 205 oflumen 204, thereby positioning coil 200 within lumen 204. In someembodiments, coil 200 can include a hook (not shown) at its distal end201 (FIG. 6C) that can hook into wall 205, further helping to positioncoil 200 within lumen 204. Eventually, bioerodible connector 212 erodessufficiently to allow coil 200 to expand away from generally tubularmember 206 at its proximal end 210 (FIGS. 6A and 6D), as well. Deliverysystem 202 is then removed from lumen 204, leaving expanded coil 200,which has a lumen 218, within lumen 204 (FIG. 6D). Referring now to FIG.6E, a stent 220 is then delivered into lumen 218 of coil 200.

Bioerodible connectors 212 and/or 216 may be formed, for example, of oneor more of the bioerodible materials described above. In certainembodiments, bioerodible connectors 212 and/or 216 can be attached tocoil 200 and/or generally tubular member 206 using an adhesive. Examplesof adhesives include acrylics, cyanoacrylate, epoxies, and polyurethane.In some embodiments, bioerodible connectors 212 and/or 216 can beattached to coil 200 and/or generally tubular member 206 usingultrasonic welding, laser welding, ultraviolet bonding, and/or heatbonding. In certain embodiments, bioerodible connectors 212 and/or 216can be attached to coil 200 and/or generally tubular member 206 bysuspending the bioerodible material of bioerodible connectors 212 and/or216 in a substrate (e.g., styrene-isobutylene-styrene) that is attachedto and/or coated on the coil and/or generally tubular member. Whilebioerodible connectors that are made of different materials have beendescribed, in some embodiments, bioerodible connectors can be made ofthe same material.

As shown in FIGS. 6A-6E, coil 200 does not include a solid conductor(e.g., a wire) connecting its proximal and distal ends. However, coil200 can still form a resonance circuit. FIG. 7 shows an enlarged view ofcoil 200. Referring to FIG. 7, coil 200 includes an insulated region 230(e.g., so that coil 200 has limited or no electrical contact with astent that is disposed within its lumen), a conductive region 232 at itsproximal end 210, and a conductive region 234 at its distal end 214.When coil 200 is disposed at a target site (e.g., within a lumen of asubject, such as lumen 204), conductive regions 232 and 234 can be inelectrical communication with each other (e.g., through blood and/orother body fluids, and/or through the structure of stent 220), so thatcoil 200 is able to carry a current.

FIGS. 8A-8D illustrate another method of delivering a coil into a lumenof a subject. As shown in FIG. 8A, a delivery system 304 includes agenerally tubular inner member 306, a tip 308 at the distal end 310 ofinner member 306, and a sheath 312 surrounding inner member 306. Sheath312 has an interior surface 314 and an exterior surface 316. On itsinterior surface 314, sheath 312 has helical grooves 318. Coil 300 isdisposed within grooves 318.

As shown in FIG. 8B, to deliver coil 300 into a lumen 302 of a subject,sheath 312 is rotated in the direction of arrow A3 while being withdrawnproximally (in the direction of arrow A4). As sheath 312 is rotated andwithdrawn, coil 300 exits sheath 312 and expands into lumen 302. In someembodiments, proximal end 324 of coil 300 can be attached to innermember 306. For example, in certain embodiments, inner member 306 canhave a hole in it, and proximal end 324 of coil 300 can be placed in thehole. In some embodiments, proximal end 324 of coil 300 can be attachedto inner member 306 with a bioerodible connector. In certainembodiments, the attachment of proximal end 324 of coil 300 to innermember 306 can limit the likelihood that coil 300 will be withdrawn withsheath 312. In some embodiments, coil 300 can become detached from innermember 306 once sheath 312 has been withdrawn from the region in whichcoil 300 is located. Eventually, the entirety of coil 300 is deliveredinto lumen 302, and delivery system 304 is removed from lumen 302,leaving expanded coil 300, which has a lumen 320, within lumen 302 (FIG.8C). Referring now to FIG. 8D, after coil 300 has been delivered intolumen 302, a stent 322 is delivered into lumen 320 of coil 300.

In some embodiments (e.g., if it is determined after partial delivery ofcoil 300 that coil 300 is being delivered to an untargeted location),coil 300 can be withdrawn back into sheath 312 by rotating sheath 312 ina direction opposite to that of arrow A3.

Like coil 200, coil 300 does not include a wire connecting its proximalend 324 and its distal end 326. However, as shown in FIG. 9, coil 300has an insulated region 328, a conductive region 330 at its proximal end324, and a conductive region 332 at its distal end 326. Thus, like coil200, coil 300 can conduct current (e.g., through blood and/or other bodyfluids, and/or through the structure of stent 322).

An electrically conductive coil, such as one of the electricallyconductive coils described above, can be formed of a relatively elasticmaterial, such as a superelastic or pseudo-elastic material (e.g., asuperelastic or pseudo-elastic metal alloy). Such materials can allowthe coil to temporarily deform and then regain its shape, withoutexperiencing a permanent deformation. Examples of superelastic materialsinclude a Nitinol (e.g., 55% nickel, 45% titanium), silver-cadmium(Ag—Cd), gold-cadmium (Au—Cd), gold-copper-zinc (Au—Cu—Zn),copper-aluminum-nickel (Cu—Al—Ni), copper-gold-zinc (Cu—Au—Zn),copper-zinc (Cu—Zn), copper-zinc-aluminum (Cu—Zn—Al), copper-zinc-tin(Cu—Zn—Sn), copper-zinc-xenon (Cu—Zn—Xe), indium-thallium (In—Ti),nickel-titanium-vanadium (Ni—Ti—V), titanium-molybdenum (Ti—Mo),titanium-niobium-tantalum-zirconium (Ti—Nb—Ta—Zr), and copper-tin(Cu—Sn). See, e.g., Schetsky, L. McDonald, “Shape Memory Alloys”,Encyclopedia of Chemical Technology (3rd ed.), John Wiley & Sons, 1982,vol. 20, pp. 726-736, for a full discussion of superelastic alloys.Other examples of materials include one or more precursors ofsuperelastic alloys, i.e., those alloys that have the same chemicalconstituents as superelastic alloys, but have not been processed toimpart the superelastic property under the conditions of use. Suchalloys are further described, for example, in PCT Application No.US91/02420.

In certain embodiments, an electrically conductive coil can be formed ofa shape memory material. Examples of shape memory materials includemetal alloys, such as Nitinol (e.g., 55% nickel, 45% titanium),silver-cadmium (Ag—Cd), gold-cadmium (Au—Cd), gold-copper-zinc(Au—Cu—Zn), copper-aluminum-nickel (Cu—Al—Ni), copper-gold-zinc(Cu—Au—Zn), copper-zinc (Cu—Zn), copper-zinc-aluminum (Cu—Zn—Al),copper-zinc-tin (Cu—Zn—Sn), copper-zinc-xenon (Cu—Zn—Xe), iron beryllium(Fe₃Be), iron platinum (Fe₃Pt), indium-thallium (In—Tl), iron-manganese(Fe—Mn), nickel-titanium-vanadium (Ni—Ti—V), iron-nickel-titanium-cobalt(Fe—Ni—Ti—Co) and copper-tin (Cu—Sn). See, e.g., Schetsky, L. McDonald,“Shape Memory Alloys”, Encyclopedia of Chemical Technology (3rd ed.),John Wiley & Sons, 1982, vol. 20, pp. 726-736. In some embodiments, anelectrically conductive coil can be formed of a shape-memory materialwith a coating over it (e.g., a biocompatible coating). The coating canact as an insulator or as a conductor. In certain embodiments, thecoating can be formed of gold (e.g., sputtered gold). In someembodiments, an electrically conductive coil can be formed of apolymeric shape-memory material in combination with at least oneconductive material. The conductive material can be, for example, in theform of a strip and/or a coating (e.g., formed by sputtering) on thepolymeric shape-memory material. As an example, in certain embodiments,an electrically conductive coil can be formed of a shape-memorypolyurethane and can have a gold coating.

While shape memory materials have been described, in some embodiments,an electrically conductive coil can be formed of one or more othermaterials, such as spring steel and/or stainless steel. In certainembodiments, an electrically conductive coil can be formed out of one ormore electrically conductive polymers. Examples of electricallyconductive polymers include polyaniline, polypyrrole, and polythiopene.

In some embodiments, an electrically conductive coil can be formed of amaterial that is more ductile than the material of a stent that is atleast partially disposed within the electrically conductive coil. Thiscan, for example, allow the coil to adapt to the expansion of the stent(e.g., by moving to accommodate the stent), and/or can limit thelikelihood of the coil restricting the expansion of the stent.

In some embodiments, an electrically conductive coil can be partially orentirely covered (e.g., coated) with an insulating material (e.g., abiocompatible insulating material). The insulating material can, forexample, help to electrically isolate the coil from a stent that is atleast partially disposed within the coil. Examples of insulatingmaterials include polymers, such as polymers having a relatively highvolume resistivity (e.g., more than about 10⁷ Ohm-cm). Examples ofpolymers that can be used as insulating materials include polyimides,polystyrenes, polyamide 12, polytetrafluoroethylene (Teflon®), expandedpolytetrafluoroethylene (e-PTFE), polyvinylidene difluoride (PVDF),polyurethanes, and silicone rubber. Additional examples of insulatingmaterials include aluminum nitride (e.g., having a volume resistivity ofabout 10¹¹ Ohm-cm) and diamond-like coatings. Diamond-like coatings aredescribed, for example, in Straumal et al., “Vacuum Arc Deposition ofProtective Layers on Glass and Polymer Substrates”, Thin Solid Films 383(2001) 224-226. Further examples of insulating materials includeheat-shrink materials (e.g., polyethylene terephthalate (PET)). In someembodiments, a heat-shrink coating on a coil can be relatively thin(e.g., can have a thickness of less than about five nanometers). Incertain embodiments, an insulating layer (e.g., a polymer insulatinglayer) can be applied to a coil using a dip-coating process and/or aspraying process. In some embodiments, the surface of an electricallyconductive coil can be oxidized to provide an insulating layer on thecoil.

Typically, an electrically conductive coil can have dimensions thatallow the coil to fit within a target site and/or to accommodate a stentwithin the lumen of the coil.

In some embodiments, a coil can have an expanded diameter of at leastabout one millimeter (e.g., at least about 1.5 millimeter, at leastabout two millimeters, at least about five millimeters, at least about10 millimeters, at least about 12 millimeters, at least about 15millimeters, at least about 20 millimeters, at least about 24millimeters, at least about 30 millimeters, at least about 35millimeters, at least about 40 millimeters), and/or at most about 46millimeters (e.g., at most about 40 millimeters, at most about 35millimeters, at most about 30 millimeters, at most about 24 millimeters,at most about 20 millimeters, at most about 15 millimeters, at mostabout 12 millimeters, at most about 10 millimeters, at most about fivemillimeters, at most about two millimeters, at most about 1.5millimeter). In certain embodiments (e.g., certain embodiments in whicha coil is adapted for use in a coronary vessel), a coil can have anexpanded diameter of about two millimeters. In some embodiments (e.g.,some embodiments in which a coil is adapted for use in an iliac vessel),a coil can have an expanded diameter of about 12 millimeters. In certainembodiments (e.g., certain embodiments in which a coil is adapted foruse in an abdominal aortic aneurysm (AAA) application), a coil can havean expanded diameter of about 24 millimeters. In some embodiments (e.g.,some embodiments in which a coil is adapted for use in an aorticapplication), a coil can have an expanded diameter of about 40millimeters. In certain embodiments, a coil can be expanded to adiameter that is at least four times as large as the diameter of thecoil when the coil is not expanded. For example, a coil may have anon-expanded diameter of about two millimeters, and an expanded diameterof about six millimeters, or may have a non-expanded diameter of about1.5 millimeters, and an expanded diameter of about 4.5 millimeters.

In certain embodiments, a coil can have a length of at least about 0.4centimeter (e.g., at least about 0.5 centimeter, at least about onecentimeter, at least about five centimeters, at least about 10centimeters, at least about 15 centimeters, at least about 20centimeters, at least about 25 centimeters), and/or at most about 30centimeters (e.g., at most about 25 centimeters, at most about 20centimeters, at most about 15 centimeters, at most about 10 centimeters,at most about five centimeters, at most about one centimeter, at mostabout 0.5 centimeter). For example, in some embodiments (e.g., someembodiments in which a coil is adapted for use with a neurovascularstent), a coil can have a length of about 0.5 centimeter. In certainembodiments (e.g., certain embodiments in which a coil is adapted foruse with an abdominal aortic aneurysm (AAA) stent and/or agastrointestinal stent), a coil can have a length of about 30centimeters.

In some embodiments, a coil can be formed of a wire having a diameter ofat least about seven microns (e.g., at least about 10 microns, at leastabout 15 microns, at least about 20 microns, at least about 25 microns,at least about 50 microns, at least about 100 microns, at least about150 microns), and/or at most about 200 microns (e.g., at most about 150microns, at most about 100 microns, at most about 50 microns, at mostabout 25 microns, at most about 20 microns, at most about 15 microns, atmost about 10 microns). In certain embodiments, a coil can be formed ofa wire having an extended length of at least about three millimeters(e.g., at least about five millimeters, at least about 10 millimeters,at least about 50 millimeters, at least about 100 millimeters, at leastabout 500 millimeters, at least about 1000 millimeters, at least about2000 millimeters, at least about 3000 millimeters, at least about 4000millimeters), and/or at most about 4800 millimeters (e.g., at most about4000 millimeters, at most about 3000 millimeters, at most about 2000millimeters, at most about 1000 millimeters, at most about 500millimeters, at most about 100 millimeters, at most about 50millimeters, at most about 10 millimeters, at most about fivemillimeters).

In some embodiments, a coil can have a pitch of at least about 14microns (e.g., at least about 25 microns, at least about 50 microns, atleast about 100 microns, at least about 150 microns, at least about 200microns, at least about 300 microns, at least about 400 microns, atleast about 500 microns, at least about 600 microns, at least about 700microns, at least about 800 microns, at least about 900 microns), and/orat most about 1000 microns (e.g., at most about 900 microns, at mostabout 800 microns, at most about 700 microns, at most about 600 microns,at most about 500 microns, at most about 400 microns, at most about 300microns, at most about 200 microns, at most about 150 microns, at mostabout 100 microns, at most about 50 microns, at most about 25 microns).The pitch of a coil is the sum of the thickness of one winding of a wireused to form the coil and the amount of space between that winding and aconsecutive winding of the wire. When the windings of a coil are flushwith each other, the pitch of the coil is equal to the thickness of onewinding of the wire that is used to form the coil and to the diameter ofthe wire that is used to form the coil.

A stent that is used in conjunction with an electrically conductivecoil, such as one of the stents described above, can be aself-expandable stent, a balloon-expandable stent, or a combination ofboth (e.g., Andersen et al., U.S. Pat. No. 5,366,504).

In some embodiments, a stent can be formed of an MRI-compatiblematerial, such as a non-ferromagnetic material. As an example, a stentcan be formed of one or more materials with a relatively low magneticsusceptibility. For example, a stent can be formed of a material (e.g.,a metal, a metal alloy) with a magnetic susceptibility of less than0.9×10⁻³ (e.g., less than 0.871×10⁻³, less than 0.3×10⁻³, less than−0.2×10⁻³). In certain embodiments, a stent can include a material witha magnetic susceptibility that is lower than the magnetic susceptibilityof stainless steel and/or Nitinol. In some embodiments, a material witha relatively low magnetic susceptibility can be unlikely to movesubstantially as a result of being exposed to MRI. Materials having arelatively low magnetic susceptibility are described, for example, inStinson et al., U.S. patent application Ser. No. 11/004,009, filed onDec. 3, 2004, and entitled “Medical Devices and Methods of Making theSame”.

In certain embodiments in which a stent is a self-expandable stent, thestent can include a relatively elastic material, such as a superelasticor pseudo-elastic metal alloy. Such materials can cause the stent to berelatively flexible during delivery, thereby allowing the stent to besafely advanced through a lumen (e.g., through a relatively tortuousvessel). Alternatively or additionally, such materials can allow thestent to temporarily deform (e.g., upon experiencing a temporaryextrinsic load), and then regain its shape (e.g., after the load hasbeen removed), without experiencing a permanent deformation, which couldlead to re-occlusion, embolization, and/or perforation of the lumenwall. Examples of such materials are provided above with reference toelectrically conductive coil materials.

In certain embodiments, a stent can include one or more materials thatcan be used for a balloon-expandable stent, such as noble metals (e.g.,platinum, gold, palladium), refractory metals (e.g., tantalum, tungsten,molybdenum, rhenium), and alloys thereof. Other examples of stentmaterials include titanium, titanium alloys (e.g., alloys containingnoble and/or refractory metals), vanadium alloys, stainless steels,stainless steels alloyed with noble and/or refractory metals,nickel-based alloys (e.g., those that contain platinum, gold, and/ortantalum), iron-based alloys (e.g., those that contain platinum, gold,and/or tantalum), cobalt-based alloys (e.g., those that containplatinum, gold, and/or tantalum), aluminum alloys, zirconium alloys, andniobium alloys. Metal alloys are described, for example, in Stinson,U.S. Patent Application Publication No. US 2005/0070990 A1, published onMar. 31, 2005.

In some embodiments, a stent can include one or more radiopaquematerials (e.g., metals, metal alloys), which can cause the stent to bevisible using X-ray fluoroscopy (e.g., allowing the stent to be trackedas it is delivered to a target site). Examples of radiopaque materialsinclude metallic elements having atomic numbers greater than 26 (e.g.,greater than 43), and/or those materials having a density greater thanabout eight grams per cubic centimeter (e.g., greater than about 9.9grams per cubic centimeter, at least about 25 grams per cubiccentimeter, at least about 50 grams per cubic centimeter).

In some embodiments, a medical device can include a material (e.g., ametal, a metal alloy) with a magnetic susceptibility of less than0.9×10⁻³ and a density of greater than about eight grams per cubiccentimeter. For example, a medical device can include platinum,tantalum, palladium, and/or molybdenum. In certain embodiments, aradiopaque material can be relatively absorptive of X-rays. For example,the radiopaque material can have a linear attenuation coefficient of atleast 25 cm⁻¹ (e.g., at least 50 cm⁻¹) at 100 keV. Examples ofradiopaque materials include tantalum, platinum, iridium, palladium,tungsten, gold, ruthenium, niobium, and rhenium. The radiopaque materialcan include an alloy, such as a binary, a ternary or more complex alloy,containing one or more elements listed above with one or more otherelements such as iron, nickel, cobalt, or titanium. The radiopaquematerial can, for example, be more radiopaque than stainless steel. Insome embodiments, the radiopaque material can be more radiopaque thaniron and/or Nitinol.

A stent can be of any desired shape and size (e.g., a coronary stent, anaortic stent, a peripheral vascular stent, a gastrointestinal stent, aurology stent, a neurology stent). Depending on the application, a stentcan have an expanded diameter of, for example, from about one millimeterto about 46 millimeters. In certain embodiments, a coronary stent canhave an expanded diameter of from about 1.5 millimeters to about sixmillimeters (e.g., from about two millimeters to about six millimeters).In some embodiments, a peripheral stent can have an expanded diameter offrom about four millimeters to about 24 millimeters. In certainembodiments, a gastrointestinal and/or urology stent can have anexpanded diameter of from about six millimeters to about 30 millimeters.In some embodiments, a neurology stent can have an expanded diameter offrom about one millimeter to about 12 millimeters. In certainembodiments, an abdominal aortic aneurysm (AAA) stent and/or a thoracicaortic aneurysm (TAA) stent can have an expanded diameter from about 20millimeters to about 46 millimeters.

While certain embodiments have been described, other embodiments arepossible.

As an example, in some embodiments, a bioerodible material that is usedto attach a coil to a delivery device can be eroded by exposure to astimulus and/or a material that is adapted to erode the bioerodiblematerial. For example, in some embodiments, a bioerodible material canbe contacted with an agent (e.g., an alcohol, hydrochloric acid, sodiumhydroxide, sodium citrate, sodium hexa-metaphosphate) that can dissolveor erode at least a portion of the bioerodible material. The agent canbe applied to the bioerodible material prior to and/or during deliveryof the coil to a target site. For example, in some embodiments in whichsodium alginate is used as a bioerodible material, at least a portion ofthe sodium alginate can be dissolved by contacting the sodium alginatewith sodium hexa-metaphosphate. In certain embodiments, an agent that isadapted to dissolve or erode a bioerodible material that is used toattach a coil to a delivery device can be added into the delivery device(e.g., into a space in the delivery device in which the coil is located)prior to and/or during delivery of the coil to a target site. In someembodiments, a change in temperature, pH, and/or pressure may be used todetach a coil from a delivery device. In certain embodiments, anexposure to energy (e.g., optical energy, electrical energy) may be usedto detach a coil from a delivery device. Attachment materials andmethods of detachment are described, for example, in Bertolino et al.,U.S. Patent Application Publication No. US 2004/0024441 A1, published onFeb. 5, 2004.

As another example, while delivery of a coil by erosion of bioerodibleconnectors has been described, in some embodiments, a coil can bedetached from a delivery device using a different method. For example,in certain embodiments, electrolytic disintegration can be used todetach a coil from a delivery device. A point of attachment between thecoil and the delivery device may be weaker than other regions of thecoil. As current flows through the coil, the current can cause the pointof attachment to electrolytically disintegrate, thereby causing the coilto become detached from the delivery device. Electrolytic disintegrationis described, for example, in Guglielmi et al., U.S. Pat. No. 5,895,385,and in Guglielmi et al., U.S. Pat. No. 5,944,714.

As an additional example, in some embodiments, an electricallyconductive coil and a wire attached to the electrically conductive coilcan both be wound around a delivery device. For example, FIG. 10 shows adelivery device 350, and an electrically conductive coil 352 and a wire354 both wound around delivery device 350. Electrically conductive coil352 and wire 354 are connected to each other, and are attached todelivery device 350 by bioerodible connectors 356 and 358. In someembodiments, after delivery device 350 has been delivered to a targetsite (e.g., a lumen of a subject), and bioerodible connector 356 and/or358 has eroded, delivery device 350 can be rotated and withdrawn todeliver electrically conductive coil 352 and wire 354 to the targetsite.

As shown in FIG. 10, in certain embodiments, a wire that is wound arounda delivery device can have fewer windings than an electricallyconductive coil that also is wound around the delivery device. As aresult, in some embodiments, when the coil and the wire are delivered toa target site, the coil may still include some windings, while the wiremay be relatively straight. In certain embodiments, a wire that is woundaround a delivery device may have some slackness so that the wire doesnot form a tight coil around the delivery device. In some embodiments,this slackness may limit the likelihood of the wire breaking when thewire is wound around the delivery device.

As a further example, in certain embodiments, a coil may be mechanicallydetached from a delivery device. For example, a coil may be detachedfrom a delivery device using a cutter, such as a cutter that can beactuated to detach a coil from a delivery device. As an example, anactuated cutter may slide between a sheath and an inner member of adelivery device, and/or along the surface of a tubular member of adelivery device, to detach a coil from the delivery device. In someembodiments, a coil can be latched onto a delivery device (e.g., aninner member of a delivery device), and can be detached from thedelivery device by being unlatched from the delivery device.

In some embodiments, a release wire can be used to mechanically detach acoil from a delivery device. As an example, FIGS. 11A and 11B show adelivery device 360 and an electrically conductive coil 362 and a wire364 wrapped around delivery device 360. Wire 364 is connected to coil362. Coil 362 and wire 364 are held onto delivery device 360 by twoloops 366 and 368 that wrap around wire 364 and through holes 370, 372,374, and 376 in delivery device 360. Loops 366 and 368 are connected toa release wire 378. Loop 366 has a weak region 380, and loop 368 has aweak region 382. When release wire 378 is pulled in the direction ofarrow A5, weak regions 380 and 382 of loops 366 and 368 can break, sothat loops 366 and 368 no longer restrain coil 362 and wire 364 ondelivery device 360. Coil 362 and wire 364 can then be delivered to atarget site. As another example, FIG. 12 shows a balloon 900 of adelivery device. A wire 902 is looped around balloon 900 such that itforms pairs of overlapping loops, including loops 904 and 906, and loops908 and 910. A release wire 909 is threaded between the loops to helprestrain the looped wire 902 against balloon 900. A third wire 912connects one end 914 of looped wire 902 to another end 916 of loopedwire 902, and includes a capacitor 918. During use, release wire 909 iswithdrawn, thereby separating the pairs of overlapping loops from eachother. Wire 902, which can have shape memory of a coil, can then expandto form that coil. Together with wire 912, wire 902 can, for example,form a resonance circuit during use.

As a further example, in some embodiments, a coil may be detached from adelivery device by exposing the coil to ultrasound. The ultrasound maycause one or more points of attachment between the coil and the deliverydevice to break, thereby causing the coil to become detached from thedelivery device in at least one region.

In some embodiments, an operator can detach a coil from a deliverydevice at a desired time (e.g., by mechanically and/or electrolyticallydetaching the coil from the delivery device).

As an additional example, while the delivery of a stent into theentirety of an electrically conductive coil has been shown, in certainembodiments, a stent may be delivered into only a portion of anelectrically conductive coil.

As another example, in some embodiments, only a portion of a stent maybe delivered into an electrically conductive coil. For example, one endof a stent may be delivered into an electrically conductive coil, whileanother end of the stent is not delivered into the electricallyconductive coil.

As a further example, in some embodiments, an electrically conductivecoil can be restrained by a sheath that does not include grooves on itsinterior surface. For example, FIGS. 13A-13C illustrate a method ofdelivering a coil 400 into a lumen 402 of a subject. As shown in FIG.13A, a delivery system 404 includes a generally tubular inner member406, a tip 408 at the distal end 410 of inner member 406, and a sheath412 surrounding inner member 406. Sheath 412 has an interior surface 414and an exterior surface 416. On its interior surface 414, sheath 412does not have any grooves. Sheath 412 restrains coil 400. As shown inFIGS. 13A-13C, coil 400 has a proximal end 401, a distal end 403, and awire 405 connecting proximal end 401 to distal end 403. Wire 405 coilsaround inner member 406.

As shown in FIG. 13B, to deliver coil 400 into lumen 402, sheath 412 iswithdrawn proximally (in the direction of arrow A6). As sheath 412 iswithdrawn, coil 400 exits sheath 412 and expands into lumen 402. As coil400 expands into lumen 402, the total number of windings of coil 400decreases, and wire 405 straightens. Eventually, the entirety of coil400 is delivered into lumen 402, and delivery system 404 is removed fromlumen 402, leaving expanded coil 400, which has a lumen 420, withinlumen 402 (FIG. 13C). In some embodiments, after coil 400 has beendelivered into lumen 402, a stent can be delivered into lumen 420 ofcoil 400.

As an additional example, in some embodiments, a coil may be attached toa delivery device by at least two bioerodible connectors (e.g., twobioerodible strips) having different thicknesses. The bioerodibleconnectors may be formed of the same bioerodible material(s) or ofdifferent bioerodible material(s). In certain embodiments, thedifference in thickness between bioerodible connectors can result in oneportion of the coil (e.g., a distal portion) being released by one ofthe bioerodible connectors before another portion of the coil (e.g., aproximal portion) is released by the other bioerodible connector.

As another example, in some embodiments, a coil can be restrained duringdelivery using a combination of the above-described systems. Forexample, in certain embodiments, a coil can be both restrained within asheath and attached to a delivery device (e.g., using one or morebioerodible connectors).

As an additional example, in some embodiments, one or more capacitiveelements and/or conductive elements can be formed in a layer-by-layerconstruction. Examples of conductive elements include electricallyconductive coils and electrically conductive traces (e.g., that are usedto interconnect electrically conductive coils and capacitive elements).Layer-by-layer deposition methods can include coating a substratematerial with charged species via electrostatic self-assembly. In someembodiments, a layer-by-layer deposition method can include usingsequential steps to provide multilayer growth on a substrate material(e.g., with intermittent rinsing between steps). During the depositionmethod, the substrate material can be exposed to one or more solutionsand/or suspensions of cationic and anionic species. The multilayergrowth can occur by depositing or adsorbing a first layer having a firstsurface charge on the substrate material, then depositing a second layeron the first layer, the second layer having a second surface charge thatis the opposite of the first surface charge, and repeating these stepsuntil a desired number of layers has been formed on the substratematerial.

In certain embodiments, a multilayer conductive element and/or amultilayer capacitive element can include multiple polyelectrolytelayers including at least one type of polyelectrolyte as a chargedspecies, and/or multiple particle layers including at least one type ofcharged particle as a charged species. Particles can include, forexample, carbon, one or more metals (e.g., gold, platinum, palladium,iridium, osmium, rhodium, titanium, tantalum, tungsten, ruthenium,magnesium, iron), metal alloys (e.g., stainless steel, Nitinol,cobalt-chromium alloys), and/or ceramics. In some embodiments, particlescan include alloys of magnesium and/or iron (e.g., including cerium,calcium, zinc, zirconium, and/or lithium). In certain embodiments,particles can include alumina, titanium oxide, tungsten oxide, tantalumoxide, zirconium oxide, and/or silica. Other examples of materials thatcan be used in particles include silicates (e.g., aluminum silicate,polyhedral oligomeric silsequioxanes (POSS)), phyllosilicates (e.g.,clays and/or micas, such as montmorillonite, hectorite, hydrotalcite,vermiculite, and/or laponite), particulate molecules (e.g., dendrimers),polyoxometallates, fullerenes, and nanotubes (e.g., single-wallnanotubes, multi-wall carbon nanotubes).

Particles are described, for example, in U.S. patent application Ser.No. ______ [Attorney Docket No. 05-01440], filed concurrently herewithand entitled “Medical Devices Having Electrical Circuits With MultilayerRegions”. Polyelectrolytes are described, for example, in Weber, U.S.Patent Application Publication No. US 2005/0261760 A1, published on Nov.24, 2005, and entitled “Medical Devices and Methods of Making the Same”;Weber et al., U.S. Patent Application Publication No. US 2005/0208100A1, published on Sep. 22, 2005, and entitled “Medical Articles HavingRegions With Polyelectrolyte Multilayer Coatings for Regulating DrugRelease”; and U.S. patent application Ser. No. ______ [Attorney DocketNo. 05-01440], filed concurrently herewith and entitled “Medical DevicesHaving Electrical Circuits With Multilayer Regions”.

In certain embodiments, a multilayered structure can include at leastone conductive layer and at least one insulating layer. The conductivelayer can include, for example, metal (e.g., gold) particles. In someembodiments, the conductive layer can be in the form of one or moreconductive traces. The conductive layer can, for example, be formed in acoil pattern, and/or can be in the form of wiring that connectselectrical components. The insulating layer can include, for example,one or more polymers and/or one or more ceramic materials.

In some embodiments, a multilayered structure can form a resonancecircuit. The resonance circuit can be used, for example, to enhance theMRI visibility of material within the lumen of an endoprosthesis, asdescribed above. In certain embodiments, a multilayered structure caninclude alternating conductive layers and insulating layers. In someembodiments, an insulating multilayered structure can includealternating polyelectrolyte-containing layers. In certain embodiments, aconductive multilayered structure can include alternatingconductive-particle-containing layers and polyelectrolyte-containinglayers.

In some embodiments, one or more of the conductive layers of amultilayered structure can be relatively thin. For example, in certainembodiments, one or more of the conductive layers of a multilayeredstructure can have a thickness of at least about 75 nanometers (e.g., atleast about 100 nanometers, at least about 150 nanometers, at leastabout 200 nanometers, at least about 250 nanometers, at least about 300nanometers, at least about 350 nanometers, at least about 400nanometers, at least about 450 nanometers) and/or at most about 500nanometers (e.g., at most about 450 nanometers, at most about 400nanometers, at most about 350 nanometers, at most about 300 nanometers,at most about 250 nanometers, at most about 200 nanometers, at mostabout 150 nanometers, at most about 100 nanometers). As the number ofconductive layers in a multilayered structure increases, theconductance, and thus the inductance, of the multilayered structure canalso increase. As a result, the size of the capacitor used inconjunction with the multilayered structure to form a resonance circuitcan decrease.

A layer-by-layer assembly process can include, for example,encapsulating conductive particles (e.g., metal particles such as gold(Au) nanoparticles) in polyelectrolyte (e.g.,poly(diallyldimethylammonium chloride) (PDDA), to form positivelycharged gold particles. A substrate can then be exposed to a colloidaldispersion of the charged particles (e.g., PDDA-coated gold particles),rinsed, exposed to an oppositely charged polyelectrolyte (e.g., asolution of poly s-119 from Sigma), rinsed, exposed to a colloidaldispersion of charged particles, rinsed, exposed to oppositely chargedpolyelectrolyte, rinsed, and so forth, until the desired number oflayers have been deposited on the substrate.

With respect to capacitive elements, in some embodiments, layer-by-layerassembly techniques, such as those described in Liu et al.,“Layer-By-Layer Ionic Self-Assembly of Au Colloids Into MultilayerThin-Films With Bulk Metal Conductivity”, Chemical Physics Letters 298(1998) 315-319, can be used to form capacitor plates. A specific exampleof a technique for layer-by-layer assembly of dielectric layers of goodresistivity, which may be positioned between the capacitor plates, isdiscussed in A. A. Antipov et al., Advances in Colloid and InterfaceScience 111 (2004) 49-61, and in references cited therein. In thistechnique, layer-by-layer-deposited poly(acrylicacid)(PAA)-poly(allylamine hydrochloride)(PAH) multilayer films arecrosslinked via heat-induced amidation. In certain embodiments,hydrophobic multilayers can be employed as dielectric films. (See, e.g.,R. M. Jisr et al., “Hydrophobic and Ultrahydrophobic Multilayer ThinFilms from Perfluorinated Polyelectrolytes,” Angew. Chem. Int. Ed. 2005,44, 782-785.)

Layer-by-layer assembly of multilayered structures (e.g., multilayeredstructures including conductive structures including metal particles) isdescribed, for example, in Liu et al., “Layer-By-Layer IonicSelf-Assembly of Au Colloids Into Multilayer Thin-Films With Bulk MetalConductivity”, Chemical Physics Letters 298 (1998) 315-319; and in U.S.patent application Ser. No. ______ [Attorney Docket No. 05-01440], filedconcurrently herewith and entitled “Medical Devices Having ElectricalCircuits With Multilayer Regions”.

As a further example, in some embodiments, a coil, a stent, and/or adelivery device can include one or more releasable therapeutic agents,drugs, or pharmaceutically active compounds, such as anti-thrombogenicagents, antioxidants, anti-inflammatory agents, anesthetic agents,anti-coagulants, and antibiotics. In certain embodiments, thetherapeutic agents, drugs, or pharmaceutically active compounds may bedisposed in a coating on the coil, stent, and/or delivery device. Insome embodiments in which a coil is attached to a delivery device usingone or more bioerodible materials, the bioerodible material(s) caninclude one or more therapeutic agents, drugs, or pharmaceuticallyactive compounds. Therapeutic agents, drugs, and pharmaceutically activecompounds are described, for example, in Phan et al., U.S. Pat. No.5,674,242; Weber, U.S. Pat. No. 6,517,888; Zhong et al., U.S. PatentApplication Publication No. US 2003/0003220 A1, published on Jan. 2,2003; and Lanphere et al., U.S. Patent Application Publication No. US2003/0185895 A1, published on Oct. 2, 2003.

As an additional example, while stents have been described, in someembodiments, an electrically conductive coil can be used in conjunctionwith one or more other types of medical devices. Examples of medicaldevices include other types of endoprostheses, such as stent-grafts,covered stents, and grafts. Grafts can be artificial grafts (e.g.,formed of polytetrafluoroethylene (PTFE) and/or polyethyleneterephthalate (PET)), and/or can be formed of autologous tissue (e.g.,vein grafts). Other examples of medical devices include filter devices;tissue-engineered vessels, valves, and organs; vena cava filters; valves(e.g., aortic valves); and abdominal aortic aneurysm (AAA) devices(e.g., AAA stents, AAA grafts). In some embodiments, tissue-engineeredvessels, valves, and/or organs can be formed on a metal support, such asan electrically conductive coil. The electrically conductive coil canboth provide support to the tissue-engineered vessel, valve, or organ,and enhance the visibility (e.g., by enhancing the resolution) of tissueunder MRI. Thus, MRI can be used, for example, to monitor neo-intimaformation and/or the build-up of soft tissue (e.g., plaque). In certainembodiments, MRI can be used to monitor the urological system and/or thereproductive system.

As a further example, in some embodiments, a coil and a stent can bedelivered to a target site (e.g., in a lumen of a subject) using thesame delivery device. The coil and the stent can be deliveredsimultaneously, or at different times. As an example, a stent can beloaded onto a balloon of a balloon catheter, and an electricallyconductive coil can be loaded over at least a portion of the stent. Theballoon catheter can then be delivered to a target site, where theballoon can be expanded to deliver both the stent and the coil into thetarget site. As another example, a balloon catheter upon which a stentand an electrically conductive coil are loaded can be delivered to atarget site, and the coil can then be expanded into the target site.Thereafter, the stent can be expanded into the target site. For example,FIG. 14A shows a delivery device 500 disposed within a lumen 502. At itsdistal end 508, delivery device 500 includes a balloon 506. A stent 504is crimped onto balloon 506, and a self-expanding electricallyconductive coil 510 is tightly wound around stent 504. Coil 510 has aproximal end 512 and a distal end 516 that are connected to each otherby a wire 513. At its proximal end 512, coil 510 is attached to stent504 by a bioerodible connector 514, and at its distal end 516, coil 510is attached to stent 504 by a bioerodible connector 517. Whenbioerodible connector 514 erodes, and delivery device 500 is rotated inthe direction of arrow A7, coil 510 is delivered into lumen 502, asshown in FIG. 14B. The rotation of coil 510 during delivery causes wire513 to rotate and form a coil as well. As coil 510 is being deliveredinto lumen 502 and/or after coil 510 has been delivered into lumen 502,bioerodible connector 517 can also erode, causing coil 510 to becomecompletely detached from stent 504. After coil 510 has been deliveredinto lumen 502 and/or detached from stent 504, stent 504 is expandedinto lumen 502 (e.g., by inflating balloon 506).

As an additional example, in certain embodiments, a balloon-expandablestent can be loaded onto a balloon of a balloon catheter, and aself-expanding electrically conductive coil can be loaded onto theballoon, over the balloon-expandable stent. The balloon can be inflated,delivering both the stent and the coil into the target site.

As a further example, in some embodiments, an electrically conductivecoil can be delivered to a target site using a balloon catheter, and astent can be delivered into a lumen of the electrically conductive coilusing a different delivery system (e.g., a different balloon catheter).

As another example, in some embodiments, an electrically conductive coilcan be wound onto a delivery device at an angle. In certain embodiments,the coil can be wound onto the delivery device manually and/or using awinding system. An example of a winding system is the 310-LC Hand Winderfrom George Stevens Manufacturing Inc. (Bensenville, Ill.). In someembodiments, a polymer sleeve can be mounted over a mandrel of a windingsystem, and a coil can then be wound around the polymer sleeve. Incertain embodiments, a coil can be loaded onto a delivery device byforming the coil at a desired expanded diameter, and then angling thecoil and loading the angled coil onto the delivery device. As an angledcoil is delivered into a target site, the coil can straighten into thetarget site, thereby causing the angle to decrease. For example, FIG.15A shows a delivery device 550 disposed within a lumen 552. Deliverydevice 550 has a longitudinal axis LA1, and includes a balloon 557. Anelectrically conductive coil 554 is wound onto balloon 557, which has adiameter d when uninflated. Coil 554 is wound onto balloon 557 at anangle α measured relative to an axis PA1 that is perpendicular tolongitudinal axis LA1. Coil 554 has an end 551 and an end 553 that areconnected to each other by a wire 555, and is attached to deliverydevice 550 by bioerodible connectors 556, 558, 560, and 562. As shown inFIG. 15B, when bioerodible connectors 556, 558, 560, and 562 erode andballoon 557 is inflated to a diameter D, coil 554 straightens out,filling lumen 552. Thereafter, and as shown in FIG. 15C, delivery device550 is withdrawn proximally from coil 554, leaving coil 554 within lumen552. As shown in FIGS. 15A-15C, coil 554 has the same number of windingsthroughout the delivery process.

FIG. 15D shows an enlarged view of a portion of delivery device 550,prior to inflation of balloon 557 and delivery of coil 554, and morespecifically shows just one section of a winding 564 of coil 554. Asshown in FIG. 15D, winding 564 forms an elliptical curve that, ifcontinued to completion, would form an ellipse E (shown partially inphantom) having a minor axis “a” and a major axis “b”. In someembodiments, angle α of coil 554 relative to axis PA1 prior to inflationof balloon 557 can be selected according to equation (1) below:(d ²)/(D ²)=sin(α)  (1)When coil 554 is wound at angle α according to the above equation, coil554 can fill lumen 552 after balloon 557 has been expanded to diameterD, and can have the same number of windings in its expandedconfiguration as in its unexpanded configuration.

As an additional example, in some embodiments, an angled coil can remainangled when delivered into a target site. For example, in certainembodiments, an angled coil (e.g., formed out of a shape-memorymaterial) may be used in an aorta. Without wishing to be bound bytheory, it is believed that by being angled, the coil may have anenhanced ability to amplify the RF field that is generated by an MRIsystem, when the coil is being delivered into the aorta. For example,the aorta may be aligned along the main axis of the MRI system. By beingangled, the coil may not be disposed at a perpendicular angle relativeto the RF waves generated by the MRI system, and may have an enhancedability to function as a receiver of the RF waves. This enhanced abilityto function as a receiver of the RF waves can cause the coil also toexhibit an enhanced ability to amplify the RF field.

As another example, in certain embodiments, a coil can include windingshaving bent regions prior to expansion of the coil into a target site.When the coil is delivered into a target site, the bent regions canstraighten, allowing the coil to fill the target site. For example, FIG.16A shows a delivery device 600 disposed within a lumen 602 andincluding a balloon 603 supporting an electrically conductive coil 604.A wire 605 connects one end 607 of coil 604 to another end 609 of coil604. As shown in FIG. 16A, in its unexpanded form, coil 604 has windings606 including loop-shaped bent regions 608. Each bent region 608restrains its neighboring bent region 608, thereby helping to maintaincoil 604 on balloon 603. Referring now to FIG. 16B, when balloon 603 isinflated, bent regions 608 straighten and coil 604 straightens intolumen 602. As shown in FIGS. 16A and 16B, coil 604 has the same numberof windings 606 in its unexpanded form as it has in its expanded form.

Coil 604 can, for example, be formed of a metal. In some embodiments,coil 604 can be formed of a relatively malleable metal, such as gold.This malleability can result in relatively easy formation of coil 604(e.g., bent regions 608). In certain embodiments, coil 604 can be formedby bending a wire to form bent regions 608, and then winding the wireinto the shape of coil 604. While bent regions 608 of coil 604 overlapwith their neighboring bent regions 608, in some embodiments, a coil caninclude bent regions that do not substantially contact each other. Incertain embodiments, the bent regions of a coil may be parallel to eachother but may not overlap with each other. In some embodiments, the bentregions of a coil can partially overlap with each other. In certainembodiments, a bent region of a coil can be nested within a neighboringbent region of the coil (e.g., when the coil is loaded onto a deliverydevice).

While a coil with windings including bent regions pointing in the samedirection has been described, in some embodiments, a coil can includewindings with bent regions pointing in different directions. Forexample, FIG. 17 shows an electrically conductive coil 650 disposed on aballoon 652 of a delivery device 654 that has been delivered into alumen 656. Coil 650 includes windings 658 having loop-shaped bentregions 660 pointing in one direction, and windings 662 havingloop-shaped bent regions 664 pointing in the opposite direction.

While coils including windings with loop-shaped bent regions have beendescribed, in certain embodiments, a coil can include one or morewindings with bent regions of a different shape. For example, FIG. 18shows an electrically conductive coil 680 disposed on a balloon 682 of adelivery device 684 that has been delivered into a lumen 686. Coil 680includes windings 688 having triangular bent regions 690.

In certain embodiments, a coil can include windings with bent regionsthat have different shapes and/or that are formed in differentdirections.

As a further example, in some embodiments, an electrically conductivecoil can include an adjustable wire that can adjust to connect two endsof the coil to each other during and/or after delivery of the coil to atarget site. For example, FIG. 19A shows a delivery device 700 disposedwithin a lumen 702 of a subject. An electrically conductive coil 704including windings 706 and a stopper 701 is disposed on delivery device700. Coil 704 also includes a wire 708 having one end 710 that isintegrally formed with coil 704, and another end 714 that includes aloop 712. Loop 712 is disposed around a winding 706 of coil 704. Twobioerodible connectors 716 and 718 connect coil 704 to delivery device700. As shown in FIG. 19B, when bioerodible connectors 716 and 718erode, coil 704 unwinds off of delivery device 700, filling lumen 702.During the unwinding of coil 704, windings 706 unwind through loop 712,until loop 712 is stopped by stopper 701. As shown in FIG. 19C, aftercoil 704 has been delivered into lumen 702, delivery device 700 can bewithdrawn from lumen 702, leaving coil 704 disposed within lumen 702.

As an additional example, in some embodiments, an electricallyconductive coil can be formed out of a wire that itself is formed out ofa coil. For example, FIG. 20 shows an electrically conductive coil 750that is formed out of a coiled wire 752. Because wire 752 is coiled,coil 750 can stretch (e.g., during expansion of coil 750 into a targetsite using a delivery device). Wire 752 can be formed of, for example,one or more metals, such as platinum and/or gold. In some embodiments,the material of wire 752 can be selected for malleability and/or forsufficient strength so that coil 750 can maintain its expanded shape ata target site. In certain embodiments, coil 750 and an endoprosthesiscan be delivered into a target site (e.g., a lumen) simultaneously(e.g., using a balloon catheter).

As a further example, in some embodiments, an electrically conductivecoil can include a polymeric coil body that is at least partially coatedwith an electrically conductive material. For example, the polymericcoil body can be imprinted with an electrically conductive ink. The inkcan be used to form a layer that is, for example, at least about twomillimeters thick and/or at most about four millimeters thick. Incertain embodiments, at least one of the components of a resonancecircuit can be formed of a polymer that is imprinted with anelectrically conductive ink. For example, a resonance circuit mayinclude a coil formed out of Nitinol, and a capacitor formed out of apolymer imprinted with an electrically conductive ink.

As an additional example, a wire connecting the ends of an electricallyconductive coil can extend within the lumen of the coil and/or outsideof the lumen of the coil. For example, FIG. 21 shows an electricallyconductive coil 800 having a lumen 802. A wire 804 connects one end 806of coil 800 to another end 808 of coil 800. Wire 804 does not extendthrough lumen 802 of coil 800. FIG. 22 shows an electrically conductivecoil 850 having a lumen 852. A wire 854 connects one end 856 of coil 850to another end 858 of coil 850. Wire 854 extends through lumen 852 ofcoil 850.

As another example, in some embodiments, an electrically conductive coilcan include two ends that are connected to each other by a coiled wire.In certain embodiments, when the electrically conductive coil isdelivered into a target site, the wire can uncoil until it is straight,and then can coil in a direction that is opposite to the direction inwhich the wire was originally coiled.

As an additional example, while coil delivery devices including sheathshave been described, in some embodiments, a coil delivery device caninclude a rolling membrane. Rolling membranes are described, forexample, in Austin et al., U.S. Patent Application Publication No. US2004/0199239 A1, published on Oct. 7, 2004, and entitled “ProtectiveLoading of Stents”, and in Vrba et al., U.S. Pat. No. 6,942,682.

As another example, in some embodiments, an electrically conductive coilcan function as an imaging coil and as a resonance circuit. For example,during delivery of the coil, and while the coil is disposed on adelivery device (e.g., a catheter), the coil can be used to provide animage of its environment under magnetic resonance imaging (MRI). Theclose proximity of the coil to the area that is being imaged can allowthe area to be imaged with relatively high resolution. Once the coil hasbeen delivered into a target site, the coil can be used as a resonancecircuit (e.g., that can enhance the visibility of material within thelumen of an endoprosthesis at the target site). As an example, FIG. 23Ashows an electrically conductive coil 950 (e.g., formed of a coiledwire, as described above) that is disposed on the balloon 952 of acatheter 954. As shown in FIG. 23A, catheter 954 has been delivered intoa lumen 955. A wire 956 connects one end 958 of coil 950 to another end960 of coil 950. One winding 962 of coil 950 includes a capacitor 964.Catheter 954 includes a shaft 966. Two electrically conductive traces968 and 970 (e.g., formed of sputtered gold) are located both on shaft966 and on balloon 952 of catheter 954. A second capacitor 972 ismounted onto shaft 966. Prior to delivery of coil 950 into lumen 955(FIG. 23A), winding 962 of coil 950 contacts traces 968 and 970, therebyforming a circuit that includes capacitors 964 and 972. During thistime, coil 950 can be used to image the environment around it under MRI.For example, an electrical current can be flowed through gold traces 964and 972, and coil 950 can function as an RF transmitter. In someembodiments, a 1.5 Tesla or 3.5 Tesla MRI system can be used inconjunction with coil 950 when coil 950 is functioning as an imagingcoil.

During delivery of coil 950, balloon 952 is inflated to deliver coil 950into lumen 955. Thereafter, and as shown in FIG. 23B, balloon 952 isdeflated and withdrawn, leaving coil 950 disposed within lumen 955. Whenballoon 952 is withdrawn, coil 950 is no longer part of a circuit thatincludes both capacitor 964 and capacitor 972. Rather, coil 950 forms aresonance circuit including capacitor 964. At this point, coil 950 canbe used as a resonance circuit, for example, to image the materialwithin a lumen of an endoprosthesis that can also be delivered intolumen 955.

As shown in FIGS. 23A and 23B, coil 950 has a larger diameter (and thus,a larger cross-sectional area) after coil 950 has been delivered intolumen 955, as compared to the diameter of coil 950 prior to delivery.The inductance of a coil such as coil 950 depends on the cross-sectionalarea of the coil, as shown in equation (2) below, in which N=number ofwindings of the coil, μ=magnetic permeability of the medium surroundingthe coil, A=cross-sectional area of the coil, and 1=length of the coil:L=(μN ² A)/(1)  (2)

The resonance frequency ω_(O) of a coil such as coil 950 is determinedbased on the inductance and the capacitance, as shown in equation (3)below:ω_(O)=1/√(LC)  (3)

Thus, the overall capacitance of a coil can be manipulated to maintainthe resonance frequency of the coil during use and delivery.Accordingly, as shown in FIGS. 23A and 23B above, when coil 950 is beingused as an imaging coil and has a relatively small cross-sectional area,coil 950 is part of a circuit including two capacitors. However, whencoil 950 has been delivered into lumen 955 and has a largercross-sectional area, the larger cross-sectional area increases theinductance of coil 950. Thus, to maintain the resonance frequency ofcoil 950, coil 950 only forms a circuit with one capacitor (capacitor964).

While FIG. 23A shows capacitor 972 mounted on catheter shaft 966, insome embodiments, a second capacitor can be located elsewhere. As anexample, in certain embodiments, a second capacitor may be locatedexternally relative to the body, but may be connected to the coil by twolead wires. As another example, in some embodiments, an electricallyconductive coil including a capacitor can be delivered to a target siteusing a delivery system including a generally tubular inner member and asheath surrounding the inner member. The coil can be loaded into thedelivery device such that the capacitor on the coil is located by thedistal section of the sheath. The sheath can include a second capacitorthat is mounted on the exterior surface of the sheath. The capacitor caninclude flat strips (e.g., two flat strips) that are embedded in and/orattached to the exterior surface of the sheath (e.g., glued to thesheath), but that also protrude to a certain extent past the distal endof the sheath (e.g., by about two millimeters). When the compressed coilis inserted into the sheath as the coil is being loaded into thedelivery device, the two flaps of the second capacitor can be foldedaround into the interior surface of the sheath. The flaps can contactthe coil when the coil is disposed within the sheath. This can allow thecoil to be used as an imaging coil during delivery to a target site, andto function as a resonance circuit once the coil has been delivered intothe target site. The use of a catheter coil for high-resolution MRIimaging is described, for example, in Zimmermann-Paul et al.,“High-Resolution Intravascular Magnetic Resonance Imaging: Monitoring ofPlaque Formation in Heritable Hyperlipidemic Rabbits”, Circulation (Mar.2, 1999), pages 1054-1061.

While maintenance of the resonance frequency of a coil by adjusting thecapacitance of the coil has been described, in some embodiments, theresonance frequency of a coil can be adjusted by changing the magneticpermeability of the environment around the coil. For example, a catheterthat is used to deliver the coil may include ferromagnetic material,which can increase the magnetic permeability of the environment aroundthe coil prior to expansion of the coil. This increase in magneticpermeability can result in an increase in the inductance of the coilprior to expansion of the coil. Ferromagnetic materials are described,for example, in Rioux et al., U.S. Patent Application Publication No. US2004/0101564 A1, published on May 27, 2004, and entitled “Embolization”.

In certain embodiments, an electrically conductive coil that is beingused as an imaging coil can be disposed on a delivery device at an angle(e.g., as described above with respect to FIGS. 15A-15D). This can, forexample, help the coil to form a relatively comprehensive image of avessel wall.

As an additional example, in some embodiments, an angled electricallyconductive coil can be retained on a delivery device by a sleeve and/ora polymer wire. The sleeve and/or polymer wire can help the coil toretain its angled shape during delivery of the coil to a target site.

For example, in certain embodiments, one or more polymer wires can bedisposed between the balloon of a delivery device and an angled coilthat is supported by the balloon. As an example, FIG. 24 shows across-sectional view of a balloon 1000 that is disposed around an innermember 1002 of a balloon catheter, and that supports an angledelectrically conductive coil 1004. As shown, balloon 1000 is in itsdeflated condition, and includes three folded regions 1006, 1008, and1010. Polymer wires 1012, 1014, and 1016 are positioned by foldedregions 1006, 1008, and 1010 of balloon 1000, respectively. Electricallyconductive coil 1004 is wrapped around balloon 1000 such thatelectrically conductive coil 1004 contacts polymer wires 1012, 1014, and1016. Additionally, a sleeve 1018 is disposed around coil 1004.

In some embodiments, polymer wires 1012, 1014, and/or 1016 can berelatively soft. For example, polymer wires 1012, 1014, and/or 1016 maybe formed of Tecothane® 75A polyether-based polyurethane (from Noveon,Inc., Akron, Ohio). In certain embodiments in which polymer wires 1012,1014, and/or 1016 are relatively soft, coil 1004 can become at leastpartially embedded in polymer wires 1012, 1014, and/or 1016. Thisembedding can cause coil 1004 to experience enhanced retention onballoon 1000, and/or can help coil 1004 to maintain its angled shapeduring delivery to a target site in a body of a subject.

In certain embodiments, polymer wires 1012, 1014, and/or 1016 caninclude a core that is formed of a relatively hard polymer, surroundedby a sleeve that is formed of a relatively soft polymer. This, can, forexample, limit the likelihood of polymer wires 1012, 1014, and/or 1016compressing axially. For example, in some embodiments, polymer wires1012, 1014, and/or 1016 can include a core that is formed of Tecothane®70D polyether-based polyurethane (from Noveon, Inc., Akron, Ohio),surrounded by a sleeve that is formed of Tecothane® 75A polyether-basedpolyurethane (from Noveon, Inc., Akron, Ohio).

Polymer wires 1012, 1014, and/or 1016 can have a cross-sectional outerdiameter of about 200 microns. In some embodiments in which polymerwires 1012, 1014, and/or 1016 include a core surrounded by a sleeve, thecore can have a cross-sectional diameter of about 100 microns.

In certain embodiments, polymer wires 1012, 1014, and/or 1016 can have atextured outer surface. This can, for example, allow coil 1004 to becomeat least partially embedded in polymer wires 1012, 1014, and/or 1016,and to thereby experience enhanced retention on balloon 1000.

Sleeve 1018, which is disposed around coil 1004, can help to limit thelikelihood of coil 1004 expanding prematurely (e.g., during delivery toa target site). In some embodiments, sleeve 1018 can include (e.g., canbe formed of) polytetrafluoroethylene (e.g., Teflon® polymer, fromDuPont) and/or high-density polyethylene (HDPE). During delivery of coil1004, sleeve 1018 can be retracted proximally to expose coil 1004. Insome embodiments, the friction between coil 1004 and polymer wires 1012,1014, and/or 1016 can limit the likelihood of sleeve 1018 disturbing theposition and/or angle of coil 1004 as sleeve 1018 is retractedproximally. In certain embodiments, at least one of polymer wires 1012,1014, and 1016 can be connected to balloon 1000. For example, in someembodiments, at least one of polymer wires 1012, 1014, and 1016 can beconnected to a polymer ring that, in turn, is connected to a proximalsection of balloon 1000. This connection between balloon 1000 andpolymer wires 1012, 1014, and/or 1016 can cause polymer wires 1012,1014, and/or 1016 to be removed with balloon 1000 when balloon 1000 isremoved from a target site (e.g., after coil 1004 has been deliveredinto the target site).

As a further example, in certain embodiments, an angled electricallyconductive coil can be retained on a delivery device by a tube and/or asleeve. The tube and/or sleeve can help the coil to retain its angledshape during delivery of the coil to a target site.

For example, in some embodiments, a soft polymer tube (e.g., formed ofTecothane® 75A polyether-based polyurethane (from Noveon, Inc., Akron,Ohio)) can be extruded and expanded (e.g., by being disposed intoluene). In certain embodiments, one or more slits can then be addedalong the central portion of the tube, without adding slits to eitherend of the tube. The tube can then be slid over a folded balloon (e.g.,of a balloon catheter), an electrically conductive coil can be woundaround the tube at an angle, and a sleeve (e.g., formed of a polymer)can be disposed over the angled coil. The coil can then be delivered toa target site in a body of a subject by proximally retracting the sleeveto expose the coil, and inflating the balloon. In some embodiments, thefriction between the coil and the tube can limit or prevent the sleevefrom disturbing the position and/or angle of the coil as the sleeve isretracted proximally.

As another example, in some embodiments, the distance between at leasttwo windings of an electrically conductive coil can be temporarilymaintained (e.g., during delivery of the coil to a target site) using,for example, an erodible material such as gelatin.

As an additional example, in certain embodiments, a stent can be coatedwith an insulating material and the insulating material can in turn beimprinted with an electrically conductive ink in the pattern of a coil.For example, a stent may be coated with a thin ceramic coating, and anelectrically conductive coil may be imprinted upon the ceramic coating.The ceramic coating can be applied to the stent using, for example,physical vapor deposition, and/or can be formed using, for example, asol-gel process.

All publications, applications, references, and patents referred to inthis application are herein incorporated by reference in their entirety.

Other embodiments are within the claims.

1. A method, comprising: delivering an electrically conductive coil intoa lumen of a subject; and delivering at least a portion of anendoprosthesis into a lumen of the electrically conductive coil.
 2. Themethod of claim 1, wherein the method comprises using a generallytubular member to deliver the electrically conductive coil into thelumen of the subject.
 3. The method of claim 2, wherein delivering theelectrically conductive coil into a lumen of a subject comprisesseparating an attached end of the electrically conductive coil from thegenerally tubular member.
 4. The method of claim 3, wherein separatingan attached end of the electrically conductive coil from the generallytubular member comprises electrolytically detaching the attached end ofthe electrically conductive coil from the generally tubular member. 5.The method of claim 3, wherein separating an attached end of theelectrically conductive coil from the generally tubular member comprisesmechanically detaching the attached end of the electrically conductivecoil from the generally tubular member.
 6. The method of claim 2,wherein the electrically conductive coil is attached to the generallytubular member by a bioerodible material.
 7. The method of claim 2,wherein during delivery of the electrically conductive coil into thelumen of the subject, the electrically conductive coil is supported bythe generally tubular member.
 8. The method of claim 7, furthercomprising separating the electrically conductive coil from thegenerally tubular member so that the electrically conductive coil nolonger is supported by the generally tubular member.
 9. The method ofclaim 8, wherein separating the electrically conductive coil from thegenerally tubular member comprises rotating the generally tubularmember.
 10. The method of claim 8, wherein separating the electricallyconductive coil from the generally tubular member comprises expandingthe electrically conductive coil into the lumen of the subject.
 11. Themethod of claim 1, further comprising viewing the endoprosthesis usingmagnetic resonance imaging.
 12. The method of claim 1, wherein theelectrically conductive coil forms a resonance circuit.
 13. The methodof claim 1, wherein the electrically conductive coil comprises aconductor connecting a first section of the electrically conductive coilto a second section of the electrically conductive coil.
 14. The methodof claim 1, further comprising connecting a proximal end of theelectrically conductive coil to a distal end of the electricallyconductive coil using a conductor.
 15. The method of claim 1, whereinthe electrically conductive coil comprises a superelastic material. 16.The method of claim 1, wherein delivering an electrically conductivecoil into a lumen of a subject comprises delivering a sheath containingthe electrically conductive coil into the lumen of the subject.
 17. Themethod of claim 16, comprising rotating the sheath to deliver theelectrically conductive coil from the sheath into the lumen of thesubject.
 18. The method of claim 16, wherein the sheath has an exteriorsurface and an interior surface that contacts the electricallyconductive coil.
 19. The method of claim 18, wherein the interiorsurface of the sheath defines at least one groove.
 20. The method ofclaim 19, wherein the interior surface of the sheath defines a helicalgroove.
 21. The method of claim 20, wherein the electrically conductivecoil is disposed within the helical groove.
 22. The method of claim 1,wherein the electrically conductive coil comprises a proximal end and adistal end, and the method comprises establishing electricalcommunication between the proximal end and the distal end.
 23. Themethod of claim 22, wherein the method comprises establishing electricalcommunication between the proximal end and the distal end without usinga solid conductor.
 24. The method of claim 1, further comprising usingmagnetic resonance imaging to view an environment surrounding theelectrically conductive coil prior to delivering at least a portion ofan endoprosthesis into a lumen of the electrically conductive coil. 25.The method of claim 1, wherein the electrically conductive coilcomprises a first capacitor, and the method further comprises flowing anelectrical current through a circuit including the first capacitor. 26.The method of claim 25, wherein the electrical circuit further comprisesa second capacitor.
 27. The method of claim 1, wherein during deliveryof the electrically conductive coil into the lumen of the subject, theelectrically conductive coil is in contact with at least one electricalcircuit component that is not a component of the electrically conductivecoil.
 28. The method of claim 1, wherein during delivery of theelectrically conductive coil into the lumen of the subject, theelectrically conductive coil resonates at the Larmor frequency of aproton in a one Tesla magnetic field, a 1.5 Tesla magnetic field, or athree Tesla magnetic field.